Referring to FIG. 1, a conventional E-paper display device 50 usually includes an E-paper display layer 54 formed on or adhered to a surface of a thin film transistor (TFT) substrate 52. Since the E-paper display layer 54 is extremely sensitive to the moisture and easily damaged due to the moisture, a protective sheet 56 made of a composite material is formed to cover the E-paper display layer 54. Then, the gap between the protective sheet 56 and the TFT substrate 52 is filled with sealant 58 to entirely separate the E-paper display layer 54 from the environment. The sealant 58 can assist the bonds between the protective sheet 56 and the TFT substrate 52 to prevent the moisture from entering the E-paper display device 50.
The protective sheet 56 may be a polymer substrate with coating treatment. Thus, the protective sheet 56 can prevent moisture, absorb ultraviolet rays, and reduce glare. The polymer substrate, for example, is made of polyethylene terephthalate (PET).
In the conventional E-paper display device 50, the protective sheet 56 is provided on the E-paper display layer 54 by adhering the protective sheet 56 to the surface of the E-paper display layer 54. During the bonding step, bubbles are easily produced between the protective sheet 56 and the E-paper display layer 54. These bubbles would affect the performance of the E-paper display device 50. Moreover, the optical characteristics of PET is not good enough so that the visible light transmittance of the protective sheet 56 is merely 85%, resulting in that it is difficult to improve the brightness or contrast of the E-paper display device 50. In addition, when the temperature increases, the polymer substrate of the protective sheet 56 may also have the problem of yellowing or deforming over time.
Therefore, an improved E-paper display device and associated manufacturing method are required to obviate the drawbacks encountered from the prior art.